1. Field of the Invention
The invention relates to electrical power network modelling methods for small perturbation stability in a power transmission network.
2. Description of Prior Art
Power system stability has been and continues to be a major concern in the system or network operation. Large and small disturbance are in two main categories for stability analysis. In the past, the small disturbance performance was evaluated by the result of a transient stability program under a small perturbation. However, this simulation result will provide a limited insight because of the difficulty in taking measurements and in ensuring sufficient stability margins for swing oscillations. The small disturbance analysis is increasingly recognized because the spontaneous nature of swing oscillations can be analyzed based on a linearized system at the steady-state operating point. An eigenvalue analysis of the system described in this application can provide many insights which are difficult to be observed in transient plots.
Many methods have been proposed to represent networks, machines and associated control equipment such as the excitation system (EXC), governor system (GOV) and power system stabilizer (PSS) as well as new components of FACTs (flexible alternating current transmission) under small perturbation. In power system, the network and components are described by equations, and the control equipments are usually represented by blocks. In all other existing techniques, the control blocks are eventually transformed into equations in order to integrate with the network/component equations to form the state space equations. However, they have the following weakness:
(i) limited flexibility, PA1 (ii) difficulty to interface with any user's new devices, PA1 (iii) restricted input/output signal selection, e.g. .DELTA.P.sub.m and .DELTA.V.sub.ref for input signals, PA1 (iv) infinite busbar assumption or restriction to a small hypothetical system, PA1 (v) difficulty for computer program implementation, PA1 (vi) limited exploitation of eigenvector analysis.